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91.
A substrain of the ascitic leucosis P-388 was obtained as a result of interchanging passages of P-388 leucosis cells in the primary cultures and abdominal cavity of mice. The tumor cells of the ascitic leucosis P-388 multiplied in the primary suspended culutres as well as in vivo. The substrain lost its hemorrhagic properties. The content of DNA and RNA in the primary cultures of P-388 doubled every 16-18 hours and the number of the cells doubled every 24-26 hours. The cells of the adapted substrain of P-388 grew also in the semiliquid agarized medium forming compact colonies by the 4th-5th day of cultivation. The primary suspended cultures of P-388 were highly sensitive to cytostatics and in particular to vinblastin and kolchamine (alkaloids). In this connection they were recommended for prescreening antitumor compounds. 相似文献
92.
A Sec14p-nodulin domain phosphatidylinositol transfer protein polarizes membrane growth of Arabidopsis thaliana root hairs
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Vincent P Chua M Nogue F Fairbrother A Mekeel H Xu Y Allen N Bibikova TN Gilroy S Bankaitis VA 《The Journal of cell biology》2005,168(5):801-812
Phosphatidylinositol (PtdIns) transfer proteins (PITPs) regulate signaling interfaces between lipid metabolism and membrane trafficking. Herein, we demonstrate that AtSfh1p, a member of a large and uncharacterized Arabidopsis thaliana Sec14p-nodulin domain family, is a PITP that regulates a specific stage in root hair development. AtSfh1p localizes along the root hair plasma membrane and is enriched in discrete plasma membrane domains and in the root hair tip cytoplasm. This localization pattern recapitulates that visualized for PtdIns(4,5)P2 in developing root hairs. Gene ablation experiments show AtSfh1p nullizygosity compromises polarized root hair expansion in a manner that coincides with loss of tip-directed PtdIns(4,5)P2, dispersal of secretory vesicles from the tip cytoplasm, loss of the tip f-actin network, and manifest disorganization of the root hair microtubule cytoskeleton. Derangement of tip-directed Ca2+ gradients is also apparent and results from isotropic influx of Ca2+ from the extracellular milieu. We propose AtSfh1p regulates intracellular and plasma membrane phosphoinositide polarity landmarks that focus membrane trafficking, Ca2+ signaling, and cytoskeleton functions to the growing root hair apex. We further suggest that Sec14p-nodulin domain proteins represent a family of regulators of polarized membrane growth in plants. 相似文献
93.
Lancaster CR Bibikova MV Sabatino P Oesterhelt D Michel H 《The Journal of biological chemistry》2000,275(50):39364-39368
It has previously been shown that replacement of the residue His L168 with Phe (HL168F) in the Rhodopseudomonas viridis reaction center (RC) leads to an unprecedented drastic acceleration of the initial electron transfer rate. Here we describe the determination of the x-ray crystal structure at 2.00-A resolution of the HL168F RC. The electron density maps confirm that a hydrogen bond from the protein to the special pair is removed by this mutation. Compared with the wild-type RC, the acceptor of this hydrogen bond, the ring I acetyl group of the "special pair" bacteriochlorophyll, D(L), is rotated, and its acetyl oxygen is found 1.1 A closer to the bacteriochlorophyll-Mg(2+) of the other special pair bacteriochlorophyll, D(M). The rotation of this acetyl group and the increased interaction between the D(L) ring I acetyl oxygen and the D(M)-Mg(2+) provide the structural basis for the previously observed 80-mV decrease in the D(+)/D redox potential and the drastically increased rate of initial electron transfer to the accessory bacteriochlorophyll, B(A). The high quality of the electron density maps also allowed a reliable discussion of the mode of binding of the triazine herbicide terbutryn at the binding site of the secondary quinone, Q(B). 相似文献
94.
Gabriele B. Monshausen Tatiana N. Bibikova Manfred H. Weisenseel Simon Gilroy 《The Plant cell》2009,21(8):2341-2356
Mechanical stimulation of plants triggers a cytoplasmic Ca2+ increase that is thought to link the touch stimulus to appropriate growth responses. We found that in roots of Arabidopsis thaliana, external and endogenously generated mechanical forces consistently trigger rapid and transient increases in cytosolic Ca2+ and that the signatures of these Ca2+ transients are stimulus specific. Mechanical stimulation likewise elicited an apoplastic alkalinization and cytoplasmic acidification as well as apoplastic reactive oxygen species (ROS) production. These responses showed the same kinetics as mechanically induced Ca2+ transients and could be elicited in the absence of a mechanical stimulus by artificially increasing Ca2+ concentrations. Both pH changes and ROS production were inhibited by pretreatment with a Ca2+ channel blocker, which also inhibited mechanically induced elevations in cytosolic Ca2+. In trichoblasts of the Arabidopsis root hair defective2 mutant, which lacks a functional NADPH oxidase RBOH C, touch stimulation still triggered pH changes but not the local increase in ROS production seen in wild-type plants. Thus, mechanical stimulation likely elicits Ca2+-dependent activation of RBOH C, resulting in ROS production to the cell wall. This ROS production appears to be coordinated with intra- and extracellular pH changes through the same mechanically induced cytosolic Ca2+ transient. 相似文献
95.
Cloning, expression, purification, and characterization of the acid alpha-mannosidase from Trypanosoma cruzi 总被引:1,自引:0,他引:1
Vandersall-Nairn AS; Merkle RK; O'Brien K; Oeltmann TN; Moremen KW 《Glycobiology》1998,8(12):1183-1194
The acid alpha-mannosidase of Trypanosoma cruzi is a broad-specificity
hydrolase involved in the catabolism of glycoconjugates, presumably in the
digestive vacuole. We have cloned the alpha-mannosidase gene from a T.cruzi
epimastigote genomic library. The alpha-mannosidase gene was determined to
be single copy by Southern analysis, and similar sequences were not
detected in genomic digests of either Trypanosoma brucei or Leishmania
donovani. The coding region was subcloned into the Pichia pastoris
expression vector pPICZ, and alpha-mannosidase activity was detected in the
medium of induced cultures. The recombinant alpha- mannosidase demonstrated
a pH optimum, inhibition by swainsonine, Km, and substrate specificity
consistent with the characteristics of the alpha-mannosidase previously
purified from T.cruzi epimastigotes. The recombinant enzyme was purified
103-fold from the culture medium of Pichia pastoris and had a native
molecular mass of 359 kDa by gel filtration. A combination of SDS-PAGE,
deglycosylation with endo H, and NH2-terminal sequencing indicates that the
enzyme is originally synthesized as a homodimeric polypeptide that is
subsequently cleaved to form a heterotetramer composed of 57 and 46 kDa
subunits. A polyclonal antibody raised to the recombinant enzyme was shown
to immunoprecipitate the alpha-mannosidase from T.cruzi cell extracts and
will be used in future immunolocalization studies.
相似文献
96.
Data on the study of antibiotic production by the representatives of Micromonospora and the use of ion exchange resins for intensification of screening antibiotic-producing organisms among Micromonospora are presented. It was found that out of 172 strains of Micromonospora tested 92 (53.5 per cent) cultures produced antibiotics, 18 of which were active against gramnegative bacteria. The use of carboxylic ion exchange resins at early microbiological stages of the screening provided an increase in the frequency of finding broad spectrum antibiotics from 10.4 to 19.7 per cent. 相似文献
97.
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100.
N. A. Kovalenko D. D. Zhdanov M. V. Bibikova V. Y. Gotovtseva 《Biochemistry (Moscow) Supplemental Series B: Biomedical Chemistry》2012,6(1):48-54
Telomerase is a ribonucleoprotein complex, which synthesizes telomeric repeats and which has been identified as a promising
target for anticancer therapy. Here we have investigated the effect of a new compound aITEL1296 on telomerase activity. aITEL1296
effectively inhibited telomerase activity; its inhibitory activity was a bit higher (IC50 = 0.19 ± 0.02 ng/mL) than that of BIBR1532, one of the most potent telomerase inhibitors known to date. In addition to telomerase
inhibition aITEL1296 activated apoptotic mechanisms and effectively suppressed proliferation of tumor cell lines (GI50 = 5.0 ± 0.2 ng/mL for most sensitive cell line LnCap) but not normal fibroblast cell line. 相似文献